Web Audio API: createMediaStreamDestination().stream - no sound - javascript

I'm stuck with a problem in which whenever I pass the stream from createMediaStreamDestination to an audio element srcObject, no audio is being played. My implementation is based off of the response posted here Combine setSinkId with stereoPanner?
Initially, I have an audio element in which I isolate the sound so that it would only play from the left speaker
const audio = document.createElement('audio');
audio.src = audioUrl;
let audioContext = new AudioContext();
let source = audioContext.createMediaElementSource(audio);
let panner = audioContext.createStereoPanner();
let destination = audioContext.destination;
panner.pan.value = -1;
source.connect(panner).connect(destination);
The above plays sound fine when I add audio.play() but I want to be able to set specifically the speakers that the audio would play out of while keeping the panner changes. Since audioContext doesn't contain any possibility of setting the sinkId yet, I created a new audio element and mediastreamdestination and passed the mediaStream into the source object
const audio = document.createElement('audio');
audio.src = audioUrl;
let audioContext = new AudioContext();
let source = audioContext.createMediaElementSource(audio);
let panner = audioContext.createStereoPanner();
let destination = audioContext.createMediaStreamDestination();
panner.pan.value = -1;
source.connect(panner).connect(destination);
const outputAudio = new Audio();
outputAudio.srcObject = destination.stream;
outputAudio.setSinkId(audioSpeakerId);
outputAudio.play();
With the new code, however, when I start up my application, the outputAudio doesn't play any sound at all. Is there anything wrong with my code that is causing the outputAudio element not to play sound? I'm fairly new to web audio api and I tried implementing the code from the mentioned stackoverflow thread but it doesn't seem to be working for me. Any help would be appreciated!

In the description of your first code block you mention that you additionally also call audio.play() to start the audio. That's also necessary for the second code block to work. You need to start both audio elements.
Generally calling play() on an audio element and creating a new AudioContext should ideally happen in response to a user action to make sure the browser's autoplay policy doesn't block the audio.
If all goes well the state of your AudioContext should be "running".

Related

Audio won't play anymore on browser after recording it with MediaRecorder

(See https://github.com/norbjd/wavesurfer-upload-and-record for a minimal reproducible example).
I'm using wavesurfer.js to display audio uploaded by the user as a waveform, and I'm trying to add a feature for recording a part of the audio uploaded.
So I've created a "Record" button (for now recording only 5 seconds of the audio) with the following code when clicking on it. I'm using MediaRecorder API :
document
.querySelector('[data-action="record"]')
.addEventListener('click', () => {
// re-use audio context from wavesurfer instead of creating a new one
const audioCtx = wavesurfer.backend.getAudioContext();
const dest = audioCtx.createMediaStreamDestination();
const audioStream = dest.stream;
audioCtx.createMediaElementSource(audio).connect(dest);
const chunks = [];
const rec = new MediaRecorder(audioStream);
rec.ondataavailable = (e) => {
chunks.push(e.data);
}
rec.onstop = () => {
const blob = new Blob(chunks, { type: "audio/ogg" });
const a = document.createElement("a");
a.download = "export.ogg";
a.href = URL.createObjectURL(blob);
a.textContent = "export the audio";
a.click();
window.URL.revokeObjectURL(a.href);
}
wavesurfer.play();
rec.start();
setTimeout(() => {
rec.stop();
wavesurfer.stop();
}, 5 * 1000);
});
When clicking on the button for recording, the wavesurfer should play (wavesurfer.play()) but I can't hear anything from my browser (but I can see the cursor move). At the end of the recording (5 seconds, set with setTimeout), I can download the recorded audio (rec.onstop function) and the sound plays correctly in VLC or any other media player.
However, I can't play audio anymore on the webpage via the browser. I can still record audio, and recorded audio can be downloaded and played correctly.
I'm wondering why audio won't play on the browser after clicking on the "Record" button for the first time. I think that this line :
audioCtx.createMediaElementSource(audio).connect(dest);
is the issue, but without it, I can't record audio.
I've also tried to recreate a new AudioContext instead of using wavesurfer's one :
const audioCtx = new AudioContext();
but it does not work better (same issue).
I've reproduced the issue in a minimal reproducible example : https://github.com/norbjd/wavesurfer-upload-and-record, so feel free to check it. Any help will be welcomed !
You don't need a separate audiocontext, but you need a MediaStreamDestination that you create using the same audiocontext (from wavesurfer.js in your case) as for the audionode you want to record, and you need to connect the audionode to that destination.
You can see a complete example of capturing audio and screen video here:
https://github.com/petersalomonsen/javascriptmusic/blob/master/wasmaudioworklet/screenrecorder/screenrecorder.js
( connecting the audionode to record is done after the recording has started on line 52 )
and you can test it live here: https://petersalomonsen.com/webassemblymusic/livecodev2/?gist=c3ad6c376c23677caa41eb79dddb5485
(Toggle the capture checkbox to start recording and press the play button to start the music, toggle the capture checkbox again to stop the recording).
and you can see the actual recording being done on this video: https://youtu.be/FHST7rLxhLM
as you can see in that example, it is still possible to play audio after the recording is finished.
Note that this example has only been tested for Chrome and Firefox.
And specifically for your case with wavesurfer:
Instead of just backend: 'MediaElement', switch to backend: 'MediaElementWebAudio',
and instead of audioCtx.createMediaElementSource(audio).connect(dest);, you can change to wavesurfer.backend.sourceMediaElement.connect(dest); to reuse the existing source from wavesurfer (but also works without this).

Web Audio audiocontext createMediaStreamSource stuttering

I want to mix different audio media streams in to one stream. I'm been doing this with Web Audio audiocontext and createMediaStreamSource.
But the final mixed audio is stuttering.
Have anyone an idea how to optimize this to avoid stuttering?
// init audio context
var audioContext = new AudioContext({ latencyHint: 0 });
var audioDestination = audioContext.createMediaStreamDestination();
// add audio streams
audioContext.createMediaStreamSource(audioStream1).connect(audioDestination);
audioContext.createMediaStreamSource(audioStream2).connect(audioDestination);
audioContext.createMediaStreamSource(audioStream3).connect(audioDestination);
audioContext.createMediaStreamSource(audioStream4).connect(audioDestination);
// get mixed audio stream tracks
var audioTrack = audioDestination.stream.getTracks()[0];
// get video track
var videoTrack = videoStream.getTracks()[0];
// combine video and audio tracks into single stream.
var finalStream = new MediaStream([videoTrack, audioTrack]);
// assign to video element
el_video.srcObject = finalStream;
You could try setting the latencyHint to 'playback' like this:
const audioContext = new AudioContext({ latencyHint: 'playback' });
This allows the browser to add a bit of latency to the audio graph which can help on underpowered devices. Setting the latencyHint to 0 on the other hand will tell the browser that it should do things as fast as possible which increases the risk of dropouts.
Having said that, the latencyHint is only a hint. The browser may very well ignore it. You can check what the browser is actually doing by inspecting the baseLatency property.
console.log(audioContext.baseLatency);

Can I record the output of an <audio> without use of the microphone?

I have an <audio> element and I'm changing the speed, start/end bounds, and pitch. I want to see if it's possible to record the audio I hear in the browser. However I don't want to just record with the microphone because of the lower quality.
I could do the same effects server-side but I'd rather not since I'd be basically duplicating the same functionality with two different technologies.
In response to a flag vote since it's "unclear what I'm asking", I'll rephrase.
I have an <audio> element playing on the page. I have some javascript manipulating the play-rate, volume, etc. I then want my browser to record the audio as I hear it. This is not the microphone. I want to create a new audio file that is as close as possible to the one playing. If it's at 75%, then the new file will be at 75% volume.
In supporting browsers, you could use the MediaElement.captureStream() method along with the MediaRecorder API.
But note that these technologies are still in active development and that current implementations are still full of bugs.
E.g, for your case, current stable FF will stop the rendering of the original media audio if you change its volume while recording... I didn't had time to search for a bug report on it, but anyway, this is just one of the many bugs you'll find.
// here we will save all the chunks of our record
const chunks = [];
// wait for the original media is ready
audio.oncanplay = function() {
audio.volume = 0.5; // just for your example
// FF still does prefix this unstable method
var stream = audio.captureStream ? audio.captureStream() : audio.mozCaptureStream();
// create a MediaRecorder from our stream
var rec = new MediaRecorder(stream);
// every time we've got a bit of data, store it
rec.ondataavailable = e => chunks.push(e.data);
// once everything is done
rec.onstop = e => {
audio.pause();
// concatenate our chunks into one file
let final = new Blob(chunks);
let a = new Audio(URL.createObjectURL(final));
a.controls = true;
document.body.append(a);
};
rec.start();
// record for 6 seconds
setTimeout(() => rec.stop(), 6000);
// for demo, change volume at half-time
setTimeout(() => audio.volume = 1, 3000);
};
// FF will "taint" the stream, even if the media is served with correct CORS...
fetch("https://dl.dropboxusercontent.com/s/8c9m92u1euqnkaz/GershwinWhiteman-RhapsodyInBluePart1.mp3").then(resp => resp.blob()).then(b => audio.src = URL.createObjectURL(b));
<audio id="audio" autoplay controls></audio>
For older browsers, you could use the WebAudio API's createMediaElementSource method, to pass your audio element media through the API.
From there, you'd be able to extract raw PCM data to arrayBuffers and save it.
In following demo, I'll use recorder.js library which does greatly help for the extraction + save to wav process.
audio.oncanplay = function(){
var audioCtx = new AudioContext();
var source = audioCtx.createMediaElementSource(audio);
var gainNode = audioCtx.createGain();
gainNode.gain.value = 0.5;
source.connect(gainNode);
gainNode.connect(audioCtx.destination);
var rec = new Recorder(gainNode);
rec.record();
setTimeout(function(){
gainNode.gain.value = 1;
}, 3000);
setTimeout(function(){
rec.stop()
audio.pause();
rec.exportWAV(function(blob){
var a = new Audio(URL.createObjectURL(blob));
a.controls = true;
document.body.appendChild(a);
});
}, 6000);
};
<script src="https://rawgit.com/mattdiamond/Recorderjs/master/dist/recorder.js"></script>
<audio id="audio" crossOrigin="anonymous" controls src="https://dl.dropboxusercontent.com/s/8c9m92u1euqnkaz/GershwinWhiteman-RhapsodyInBluePart1.mp3" autoplay></audio>
As Kaiido mentions in his answer, captureStream() is one way of doing it. However, that is not fully supported in Chrome and Firefox yet. MediaRecorder does also not allow for track set changes during a recording, and a MediaStream coming from captureStream() might have those (depends on the application) - thus ending the recording prematurely.
If you need a supported way of recording only audio from a media element, you can use a MediaElementAudioSourceNode, pipe that to a MediaStreamAudioDestinationNode, and pipe the stream attribute of that to MediaRecorder.
Here's an example you can use on a page with an existing audio element:
const a = document.getElementsByTagName("audio")[0];
const ac = new AudioContext();
const source = ac.createMediaElementSource(a);
// The media element source stops audio playout of the audio element.
// Hook it up to speakers again.
source.connect(ac.destination);
// Hook up the audio element to a MediaStream.
const dest = ac.createMediaStreamDestination();
source.connect(dest);
// Record 10s of audio with MediaRecorder.
const recorder = new MediaRecorder(dest.stream);
recorder.start();
recorder.ondataavailable = ev => {
console.info("Finished recording. Got blob:", ev.data);
a.src = URL.createObjectURL(ev.data);
a.play();
};
setTimeout(() => recorder.stop(), 10 * 1000);
Note that neither approach works with cross-origin audio sources without a proper CORS setup, as both WebAudio and recordings would give the application the possibility to inspect audio data.

Chrome analyse all audio from web page

Does anyone know how to create a MediaElementSource or any other object that can be used to send ALL sound data that is being played on a webpage through an Analyser from createAnalyser()? I want to be able to use the Analyser without knowing where exactly the sound is coming from.
EDIT: I have accomplished what I wanted but not by capturing all audio. The following block gets you an analyser on a Google Play Music player page (only tested from my library, not the store).
ctx = new (window.audioContext || window.webkitAudioContext);
source = iVisual.ctx.createMediaElementSource($('audio')[0]);
analyser = iVisual.ctx.createAnalyser();
As the audio elements are not supposed to be playing at the same time, but if you still want to do it with all audio elements, I will provide you some code sample to do it. Here's the for loop that runs for every audio file you have, which it will create an audio element for with the appropriate source, and then create a sourcenode for that (createMediaElementSource), and connect that sourcenode to the analyser.
onload = function () { //this will be executed when the page is ready
window.audioFiles = ['audio1.mp3', 'audio2.mp3',...]; //the array with all audio files
window.AudioContext = window.AudioContext || window.webkitAudioContext;
context = new AudioContext();
analyser = context.createAnalyser();
analyser.connect(context.destination);
//now we take all the files and create a button for every file
sources = []; //we create an array where we store all the created sources in.
for (var x in audioFiles) {
var elem = document.createElement('audio'); //create an audio element
elem.src = audioFiles[x]; //append the specific source to it.
sources[x] = context.createMediaElementSource(elem); //create a mediasource for it
sources[x].connect(analyser); //connect that to the analyser
}
}

chrome audio analyzer breaking on audio switch

I'm creating an audio visualizer with webgl, and have been integrating soundcloud tracks into it. I want to no be able to switch tracks, but I can either get my visualizer to work and the audio to break, or I can get the audio to work and the visualizer to break.
The two ways that I've been able to make it work are
Audio working
delete audio element
append new audio element to body
trigger play
Visualizer working
stop audio
change source
trigger play
When I have the visualizer working, the audio is totally messed up. The buffers just sound wrong, and the audio has artifacts in it (noise, beeps and bloops).
When I have the audio working, when I call analyser.getByteFrequencyData, I get an array of 0's. I presume this is because the analyser is not hooked up correctly.
The code for the audio working looks like
$('#music').trigger("pause");
currentTrackNum = currentTrackNum + 1;
var tracks = $("#tracks").data("tracks")
var currentTrack = tracks[parseInt(currentTrackNum)%tracks.length];
// Begin audio switching
analyser.disconnect();
$('#music').remove();
$('body').append('<audio id="music" preload="auto" src="'+ currentTrack["download"].toString() + '?client_id=4c6187aeda01c8ad86e556555621074f"></audio>');
startWebAudio(),
(I don't think I need the pause call. Do I?)
when I want the visualizer to work, I use this code
currentTrackNum = currentTrackNum + 1;
var tracks = $("#tracks").data("tracks")
var currentTrack = tracks[parseInt(currentTrackNum)%tracks.length];
// Begin audio switching
$("#music").attr("src", currentTrack["download"].toString() + "?client_id=4c6187aeda01c8ad86e556555621074f");
$("#songTitle").text(currentTrack["title"]);
$('#music').trigger("play");
The startWebAudio function looks like this.
function startWebAudio() {
// Get our <audio> element
var audio = document.getElementById('music');
// Create a new audio context (that allows us to do all the Web Audio stuff)
var audioContext = new webkitAudioContext();
// Create a new analyser
analyser = audioContext.createAnalyser();
// Create a new audio source from the <audio> element
var source = audioContext.createMediaElementSource(audio);
// Connect up the output from the audio source to the input of the analyser
source.connect(analyser);
// Connect up the audio output of the analyser to the audioContext destination i.e. the speakers (The analyser takes the output of the <audio> element and swallows it. If we want to hear the sound of the <audio> element then we need to re-route the analyser's output to the speakers)
analyser.connect(audioContext.destination);
// Get the <audio> element started
audio.play();
var freqByteData = new Uint8Array(analyser.frequencyBinCount);
}
My suspicion is that the analyzer isn't hooked up correctly, but I can't figure out what to look at to figure it out. I have looked at the frequencyByteData output, and that seems to be indicative of something not being hooked up right. The analyser variable is global. If you would like more reference to the code, here's where it is on github
You can only create a single AudioContext per window. You should also be disconnecting the MediaElementSource when you're finished using it.
Here's an example that I used to answer a similar question: http://jsbin.com/acolet/1/

Categories

Resources